That squeak may be the compressor clutch.
You can probably eliminate the squeak by cleaning the compressor clutch with some brake cleaner. The compressor shaft seal is the most common leak point. When the refrigerant leaks out there, it brings oil with it. That oil gets flung onto the clutch plates, affecting its grab ability.
If you are going to service it yourself, shoot me a PM with your e-mail address. I'll send you a procedure for AC servicing, using a thermometer in the outlet duct vent.
If the drag you feel is excessive, your compressor may be on its last legs. If it has been serviced in the past, it may just need oil added with the refrigerant this time.
It could also be as simple as a stretched serpentine belt or a weak tensioner (and you are hearing the belt squeal when the clutch engages).
2000 2.5 MO5D 4.10 one-wheel drive DD - gave to my older son
1990 STX 87 2.9 going in.....Junked it
2000 3.0 4WD M05D 4.10 S-cab Off-Road package with 235-75-15" tires, hotrod DD, lol